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<title>Computing bounds on poly_ints (GNU Compiler Collection (GCC) Internals)</title>

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<h3 class="section" id="Computing-bounds-on-poly_005fints-1"><span>10.6 Computing bounds on <code class="code">poly_int</code>s<a class="copiable-link" href="#Computing-bounds-on-poly_005fints-1"> &para;</a></span></h3>

<p><code class="code">poly_int</code> also provides routines for calculating lower and upper bounds:
</p>
<dl class="table">
<dt>&lsquo;<samp class="samp">constant_lower_bound (<var class="var">a</var>)</samp>&rsquo;</dt>
<dd><p>Assert that <var class="var">a</var> is nonnegative and return the smallest value it can have.
</p>
</dd>
<dt>&lsquo;<samp class="samp">constant_lower_bound_with_limit (<var class="var">a</var>, <var class="var">b</var>)</samp>&rsquo;</dt>
<dd><p>Return the least value <var class="var">a</var> can have, given that the context in
which <var class="var">a</var> appears guarantees that the answer is no less than <var class="var">b</var>.
In other words, the caller is asserting that <var class="var">a</var> is greater than or
equal to <var class="var">b</var> even if &lsquo;<samp class="samp">known_ge (<var class="var">a</var>, <var class="var">b</var>)</samp>&rsquo; doesn&rsquo;t hold.
</p>
</dd>
<dt>&lsquo;<samp class="samp">constant_upper_bound_with_limit (<var class="var">a</var>, <var class="var">b</var>)</samp>&rsquo;</dt>
<dd><p>Return the greatest value <var class="var">a</var> can have, given that the context in
which <var class="var">a</var> appears guarantees that the answer is no greater than <var class="var">b</var>.
In other words, the caller is asserting that <var class="var">a</var> is less than or equal
to <var class="var">b</var> even if &lsquo;<samp class="samp">known_le (<var class="var">a</var>, <var class="var">b</var>)</samp>&rsquo; doesn&rsquo;t hold.
</p>
</dd>
<dt>&lsquo;<samp class="samp">lower_bound (<var class="var">a</var>, <var class="var">b</var>)</samp>&rsquo;</dt>
<dd><p>Return a value that is always less than or equal to both <var class="var">a</var> and <var class="var">b</var>.
It will be the greatest such value for some indeterminate values
but necessarily for all.
</p>
</dd>
<dt>&lsquo;<samp class="samp">upper_bound (<var class="var">a</var>, <var class="var">b</var>)</samp>&rsquo;</dt>
<dd><p>Return a value that is always greater than or equal to both <var class="var">a</var> and
<var class="var">b</var>.  It will be the least such value for some indeterminate values
but necessarily for all.
</p></dd>
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